Having learnt Russian, and become familiar with much of the basic astronaut training, he moved to Star City, Moscow in 1991, where he learnt the necessary skills to take part in Soyuz missions to the Mir space station (although he has still never taken part in a Soyuz mission). In 1992 he joined the European astronaut initiative, which would eventually (in 1998) become the fully operational European Astronaut Corps.

As part of his work as a European astronaut, he was transferred to the NASAJohnson Space Center in 1992, in order to train for Shuttle missions. Although the training is fairly intensive at Johnson, he still found time to oversee the design of a robotics display system for the Shuttle and the ISS that would allow for the safe and accurate manipulation of equipment such as the robotic arm without the astronaut having to leave the safety of the shuttle.

Finally, into space…

On 3 November, 1994, Clervoy began his first spaceflight, as part of the NASA STS-66 shuttle flight. He was there to deploy the CRISTA-SPAS atmospheric research satellite, which he did using the robotic arm of the shuttle (using, of course, the software system he had helped to design). The mission lasted until 14 November, during which time the shuttle made 175 orbits of the Earth.

Three years later, and Clervoy was off again, this time on flight STS-84 to the Mir Space Station. The mission began on 15 May, 1997, and is a very good example of international cooperation in space, since he was a Frenchman representing Europe on an American flight to a Russian space station. Whilst there, the shuttle team transferred 4 tons of scientific equipment onto the Mir station, and completed over 20 experiments, mainly related to the SPACEHAB module. Clervoy also took the opportunity to train as a contingency spacewalker, which basically means that he completed a spacewalk from Mir, just to see how it all worked. The team returned to Earth on 24 May.

Clervoy's final (thus far) flight began on 19 December 1999, again on the Shuttle, as part of flight STS-103. The mission was to repair and service the Hubble Space Telescope (HST), which involved the direct replacement of several gyroscopes onboard the telescope. To accomplish this, Clervoy was assigned to the robotic arm (since by now he was something of an expert at operating it), and also manoeuvred the other astronauts during the three spacewalks that were required to repair Hubble.